The present invention relates generally to switching amplifiers and more specifically to a variable frequency switching amplifier.
Switching amplifiers, such as, for example, class D audio amplifiers have associated with them a potentially high level of radiated energy at multiples of the switching frequency. This radiated switching energy can result in electro-magnetic interference (EMI) issues in adjacent circuitry. This can be particularly troublesome when trying to package the switching amplifier with a radio tuner, such as in an audio-video (AV) receiver. Currently, careful layout and filter design, coupled with shielding, is used to reduce the radiation. For example, the tuner is placed at a far enough distance from the switching amplifier so as to reduce the effects of radiation. Also, heavy shielding may be used to minimize the radiation. However, these solutions become costly and some switching energy, regardless of placement, shielding, or filtering will still be present. Therefore, a need exists for a low cost method for enabling a switching amplifier to be in proximity to a tuner without corrupting the received signal.